Most Informative Initial Investigation in Abdominal Trauma
Ultrasound (FAST - Focused Assessment with Sonography for Trauma) is the most informative initial investigation for abdominal injuries. 1
Rationale for FAST as First-Line Investigation
FAST examination offers several critical advantages in the initial assessment of abdominal trauma:
- Rapid and non-invasive: Can be performed during primary survey without delaying resuscitation efforts 1
- High diagnostic accuracy: Specificity of 96-100% and overall accuracy of 92-99% for detecting hemoperitoneum 1
- Point-of-care application: Can be performed in the resuscitation area, avoiding patient transport 1
- Triage capability: Helps determine need for immediate surgery in hemodynamically unstable patients with positive findings 1
Diagnostic Performance of FAST
- Sensitivity: 74-76% for detecting intraperitoneal free fluid 1, 2
- Specificity: 84-96% 1, 2
- Accuracy: 79% (95% CI, 70.01-86.38%) 2
- A negative FAST can reliably rule out significant hemoperitoneum (>500ml) 1
Comparison with Other Modalities
CT Scan (Option A)
- Secondary investigation for hemodynamically stable patients 1, 3
- Time-consuming and requires patient transport from resuscitation area 1
- Inappropriate for hemodynamically unstable patients 1
- Superior for characterizing specific organ injuries and detecting retroperitoneal injuries 3
Diagnostic Peritoneal Lavage (Option B)
- Invasive procedure with potential complications 1
- Largely replaced by FAST in modern trauma protocols 1
- Only indicated when ultrasound is unavailable or results are equivocal in unstable patients 3
Plain Radiography (Option D)
- Limited sensitivity for abdominal injuries 1
- Cannot reliably detect free fluid or solid organ injuries 1
- Significantly inferior to both FAST and CT for abdominal trauma evaluation 1
Important Limitations and Caveats
- FAST has limitations in detecting specific organ injuries 1
- Up to 29% of abdominal injuries may be missed if FAST is used as the sole diagnostic tool 4
- Negative FAST does not exclude low-grade solid visceral injuries 2
- Clinical risk factors should be considered with negative FAST results to avoid missed injuries 4
Clinical Algorithm for Abdominal Trauma Assessment
- Initial assessment: Perform FAST examination for all patients with suspected abdominal trauma
- Positive FAST + hemodynamic instability: Proceed to immediate surgery
- Positive FAST + hemodynamic stability: Proceed to CT scan for injury characterization
- Negative FAST + concerning mechanism or exam: Proceed to CT scan
- Negative FAST + stable patient + no concerning findings: Consider observation with serial examinations